Gene expression profiling in differential cognitive outcomes in aging: CA3

Functional alterations in medial temporal lobe structures, particularly the hippocampus, are central to age-related deficits in episodic memory. Research in aging laboratory animals has characterized physiological and cellular alterations in the hippocampus that occur in association with the presence and severity of such cognitive impairment. The current study compares alterations across hippocampal subregions by gene expression profiling in a rat model that closely mirrors individual differences in neurocognitive features of aging humans across a spectrum of outcomes, including both impaired memory and preserved function. Using mRNA profiling of the CA1, CA3 and dentate gyrus subregions, we have distinguished between gene groups and pathways related to chronological age and those specifically associated with impaired or preserved cognitive ability in aged rats. We confirmed earlier reported changes in gene groups related to inflammation and oxidative stress in multiple subregions and found these to be more associated with chronological age than cognitive function per se. The CA3 profile was best able to segregate aged impaired, aged unimpaired and young subject groups from each other. Characterization of gene changes that distinguished preserved from impaired function among the aged animals found altered expression of synaptic plasticity and neurodegenerative disease-related genes. Together these gene changes suggest recruitment of adaptive mechanisms that mediate synaptic plasticity to maintain function and structural integrity in aged unimpaired rats that does not occur in aged impaired animals.

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Haberman RP, Colantuoni C, Stocker AM, Schmidt AC, Pedersen JT, Gallagher M